Abstract
We have tried to isolate genes involved in shoot gravitropism by means of microarray. Gene expression profiles of Arabidopsis mutants, sgr1/scr, sgr7/shr and eal1, have been compared to those of wild type, and we focused several genes named DGE (DOWN-REGULATED GENE IN EAL1). These three mutants lose shoot gravitropism because of defects in formation of endodermis that is the gravity sensing tissue of shoot. We have demonstrated that DGE1 homologous to Oryza sativa LAZY1 is involved in gravitropism of Arabidopsis stem.
Here, we analyzed DGE2 encoding a protein that has a short homologous region to DGE1. It is conserved in angiosperm although DGE2 has no known functional domains or motifs. DETL (DGE TWO-LIKE GENE) that has 54% identity to DGE2 is found in Arabidopsis genome. We analyzed T-DNA insertion mutants for DGE2 and DETL. Since lateral roots of dge2 detl double mutant tend to elongate horizontal direction, these genes are expected to be involved in root gravitropism. In addition, gravitropic response of shoot, hypocotyl and root in dge1 dge2 detl triple mutant dramatically reduced. Now we are carrying out further physiological analysis of the triple mutant.
